so at the end of last summer my rims were concave from wear from my v-brakes. the front was a little more worn and i thought it could be really dangerous if the front blew out durnig a descent, so i replaced it.
i neglected the back and got the bike out last week (rode the hardtail during the winter) and noticed that i needed to replace the rim soon.
so about 15km into our ride on a rooty downhill section: BOOM! the rear rim completely exploded. anyway, it was no big deal and luckily a friend lived nearby and rode back and picked up another wheel, spin off the cassette and put on mine and i was ready to ride again.
anyway, i had heard that the rim could explode if the braking surface gets too thin from braking, and yes, it's true. the whole bike was new end of March 2002 and i rode 3800km and 65,000meters vertical and BOTH rims were trashed... makes me think next time i might actually consider disc brakes...
i've attached 2 photos of the blown out rim: